1. Field of the Invention
The invention relates to a bicycle frame having a height-adjustable saddle pillar according to the claims and a method for its assembly.
2. Description of the Related Art
Various approaches are known for bicycle frames having a height-adjustable saddle pillar.
In simple solutions, a saddle tube having a saddle fastened thereon is clamped in a seat tube of a bicycle frame. For adjustment, the clamp may be released, the saddle and the saddle tube both adjusted in height, and the clamp may be then re-engaged.
There are furthermore known solutions where a saddle pillar having an adjustable length is clamped in the seat tube of the bicycle frame.
A saddle pillar suited in this regard is known, e.g., from DE 20 2007 014 515 U1 or WO 2006/039195 A2. These documents disclose saddle pillars where the saddle is fastened on a telescope-type pipe arrangement having a frame-side outer tube and a saddle-side inner tube guided in the outer tube. The inner tube is in operative connection with a separating piston separating two pressure chambers from each other. In the case of the known solutions, these two pressure chambers are filled with a non-compressible medium such as oil, for example. In order to adjust the length of the saddle pillar, a valve arranged in the separating piston may be adjusted in a direction from the saddle by means of an adjusting lever so as to open a pressure medium connection between the two above-mentioned pressure chambers. The separating piston arrangement and thus the inner tube is subjected to the pressure in one of the pressure chambers—termed the positive chamber—in the extending direction and to the pressure in the other pressure chamber—termed the negative chamber—in the lowering direction. Here the effective surfaces of the separating piston arrangement are configured such that the force component acting upwardly in the extending direction is greater than the force component acting in the retracting direction, so that the inner tube is biased in the extending direction.
While the pressure medium connection is open, the inner tube may then be pushed into the outer tube by the rider's weight in order to change the saddle height, for example when going downhill, with pressure medium being displaced from the pressure chamber being diminished in size via the opened pressure medium connection into the pressure chamber being enlarged in size. Fixing the saddle pillar in a predetermined relative position is effected by closing the pressure medium connection, so that the exchange of pressure medium between the two pressure chambers filled with a non-compressible medium is then inhibited. In the known solutions, a kind of air spring which is formed by the volumes of air formed in the inner tube and/or in the outer tube is furthermore associated to the pressure chambers.
On the one hand it is a drawback of these known solutions including two pressure media (air, oil) that they have a very complicated construction inasmuch as a multiplicity of pressure chambers must be formed and selected in accordance with the axial length and the diameter of the saddle pillar. Moreover considerable expenditure for sealing is required in order to separate the two pressure media from each other.
Another length-adjustable saddle pillar is shown in document DE 10 2009 010 170 A1. It has an outer tube and an inner tube displaceable in the latter, wherein a separating piston delimiting a positive chamber and a negative chamber is arranged between the outer and inner tubes. A pressure medium connection between the positive chamber and the negative chamber may be closed by means of a closure member. This closure member may be an elastomer ring and may be configured such as to connect inner tube and outer tube with each other by frictional connection or form-fit in the closed position, i.e., while the pressure medium connection is blocked.
It is a drawback of such bicycle frames including an adjustable saddle pillar that in addition to the seat tube of the frame an outer tube of the saddle pillar received therein and an inner tube of the saddle pillar in turn received in the former are necessary. This amounts to a considerable weight and a small adjustment range of the frame including an adjustable saddle pillar.